Conventionally, researches on techniques for correcting the data error in the communication path have been advanced in various quarters. Some techniques have capabilities close to the Shannon limit.
Particularly, in a mobile communication, since an error characteristic in the communication path changes significantly, a very strong error correction is required.
As to the error correction techniques, retransmission techniques such as ARQ (Automatic Repeat Request) and the like, and FEC (Forward Error Correction) techniques are known. The ARQ techniques are that for performing the error correction by requesting a transmitter to retransmit data which had an error after being received (hence the techniques are classified into backward). The FEC techniques are that for previously devising the data to be transmitted and received so as to transmit reliable data and remove the error at a receiver (hence the techniques are forward). It should be noted that it is common to use the FEC and the ARQ simultaneously in a data communication, and to use the FEC only when a simultaneous processing on sounds and images is required.
However, in a transmission and reception device using the ARQ and the like, the more retransmissions are increased, the more a transmission efficiency is decreased. Moreover, in the transmission and reception device using the ARQ and the like, it is difficult to transmit and receive voice data or image data transmitted through a telephone call or streaming, due to necessity of the simultaneous processing.
For this reason, with respect to the data communication for e-mails and the like, and the transmission of the voice data or the image data, a transmission and reception device using the FEC techniques and the like has been proposed for restoring the received data as far as possible without retransmitting the data by performing the error correction for the received data, as described in Japanese Patent Laid-Open No. 2002-3444413 (pages 6 to 8, FIG. 1). This transmission and reception device performs the error correction using block codes or convolution codes.
However, in the transmission and reception device using the conventional FEC techniques, computation of the error correction is so complex that computation processes are increased. For this reason, in such a transmission and reception device, a significant memory capacity is also required for the computation.
Moreover, the transmission and reception device of a FEC method causes a disadvantage in which on the contrary more errors are occurred when the data errors increase in the communication path beyond a processing capacity for the error correction.
Particularly, in the communication such as a sound call, such a disadvantage is not preferable. Since the sound has many factors to be captured in a human sense, it is more important to be able to recognize which words are spoken in the sound even including some noises. In other words, if the FEC causes many more errors, data interpolation, repeat or discard (missing) and the like are performed. This process is referred to as Bad Frame Masking process. When this Bad Frame Masking process occurs frequently, the contents itself of the call would be likely to be inaudible.